Continuous casting mold having multiple inserts through the casting surface wall

ABSTRACT

In a continuous-casting mold the wall defining an open-ended mold cavity has inserts therethrough at spaced intervals. The inserts are made of a material, such as copper, having high heat conductivity while the wall is made of a material, such as steel, which has lower heat conductivity. The ends of the inserts are exposed respectively at the casting surface of the mold cavity and in a conduit through which a coolant is circulated in contact with the wall.

United States Patent Irving Rossi 2,128,943 9/1938 Hudson 164/283 X 3,464,483 9/1969 Cofer et al..... 249/135 X 2,479,191 8/1949 Williams et a1. 164/348 X FOREIGN PATENTS 428,615 5/1935 Great Britain 249/135 708,632 5/1954 Great Britain.... 164/283 558,667 3/1957 Italy 164/348 OTHER REFERENCES Marks Mechanical Engineers Handbook, Sixth Ed., 1958 .TJ 151M37 c.9.p.96

Primary Examiner-R. Spencer Annear AttorneySandoe, Neill, Schottler & Wikstrom ABSTRACT: In a continuous-casting mold the wall defining an open-ended mold cavity has inserts therethrough at spaced intervals. The inserts are made of a material, such as copper, having high heat conductivity while the wall is made of a material, such as steel, which has lower heat conductivity. The ends of the inserts are exposed respectively at the casting surface of the mold cavity and in a conduit through which a coolant is circulated in contact with the wall.

PATENTED nun 2:911

INVENTOR. IRVING ROSSI ATTORNEYS CONTINUOUS CASTING MOLD HAVING MULTIPLE INSERTS THROUGH THE CASTING SURFACE WALL The present invention relates to molds for the continuous casting of metal, such as steel. In particular the invention is a mold structure which provides improved cooling and solidification of the metal being cast.

In continuous casting molten metal is poured in one end of an open-ended mold cavity. The mold is cooled by circulating water or other suitable coolant through or in contact with the walls of the mold so that the periphery of molten metal in the mold solidifies to form a strand having a solidified shell around a still-molten core. The strand is withdrawn from the other end of the mold cavity and further cooled to solidify the strand completely. As the strand is withdrawn, additional molten metal is poured into the mold cavity to maintain the level of metal substantially constant thereby to enable the casting process to proceed continuously.

In conventional continuous-casting molds for steel the wall or lining of the mold defining the mold cavity are customarily made of copper which provides good heat conduction away from the mold cavity, and water or other coolant circulated through the mold walls carries the heat out of the mold for maintaining the casting surfaces of the mold cavity sufficiently cool for the strand formation to proceed continuously. However, if the rate of heat extraction is too high particularly at the level in the mold at which the solidified shell first forms the temperature at the periphery of the shell will be so low relative to the high temperature of the stillmolten core that the temperature differential causes the shell to bulge inward thereby producing one or more gaps between the surface of the mold cavity and the surface of the shell.

It is an object of the present invention to provide a continuous-casting mold which is adapted to avoid the aforementioned bulging.

This and other objects are achieved by a mold in accordance with the present invention wherein the wall or lining, which defines the mold cavity, is made of a metal having lower heat conductivity than copper with inserts of copper or other metal having a similar high heat conductivity. These inserts are mounted through the wall or lining at spaced intervals with one end of each insert exposed on the surface of the cavity and the other end exposed in a chamber or passage in the mold through which the coolant circulates. In addition, in a preferred form relatively low heat conductivity material of which the wall or lining is made is a wear resistant metal such as steel.

With this construction, the rate of heat extraction from the metal varies around the circumference of the cavity surface and is highest at the inserts. Solidification of the periphery of the metal in the cavity is, therefore, more rapid in the metal adjacent to the inserts than in the metal adjacent to other areas of the mold. In conventional continuous-casting molds, however, the heat conductivity through the cavity wall is substantially uniform around the circumference of the cavity, and the periphery of the metal solidifies at about the same rate at all points around the circumference of the cavity.

The mold structure of this invention is particularly adapted for continuous-casting molds having open-ended mold cavities and is described herein with reference to such molds. It will be appreciated, however, that this mold structure would also be useful for any types of mold in which it is desired to continuously extract heat from metal through a wall defining the casting surface. I

Further objects, advantages and features of the mold construction of this invention will be understood from the following detailed description of illustrative embodiments which are depicted in the accompanying drawings in which:

FIG. 1 is a vertical section through an open-ended continuous-casting mold embodying heat transfer structure in accordance with this invention;

FIG. 2 is an enlarged section along the line 2-2 of FIG. 1;

FIG. 3 is an enlarged section through a mold wall showing one form of an insert in accordance with the invention;

FIG. 4 is a section through a mold wall showing another form of insert;

FIG. 5 is an elevation along the line 55 of FIG. 4; and

FIG. 6 is alsection through a mold wall showing still another form of insert.

Referring to the drawings, FIG. 1 illustrates a continuouscasting mold 10 having an open-ended mold cavity II defined by a wall 12. The cross-sectional shape of the cavity 11 may be round, square, rectangular, dog bone or any other shape desired, as determined by the cross-sectional shape desired for the casting to be produced. The wall 12 is cooled by water, or other suitable coolant circulated in contact with the outer surface of the wall 12 through a chamber or conduit I3 which may be provided by a jacket I4 attached around the outside of wall 12. The coolant, from a source not shown, passes into and out of the conduit 13, respectively through an inlet I5 and outlet 16, and may be circulated by conventional pumping means, not shown.

For casting, molten metal is poured in the upper end of the mold cavity 11, and the cooled wall 12 continuously extracts heat from the periphery of the metal which is thereby solidified to form a cast strand I7 having a solidified shell 18 around a still molten core 19. The strand I7 is withdrawn from the lower end of the cavity 11 as metal is poured in the upper end for the casting to proceed continuously. After leaving the mold cavity 11, the strand 17 is further cooled by suitable means known in the art to solidify it completely.

In accordance with this invention the wall 12 has inserts 20 mounted therethrough at spaced intervals with one end of each insert exposed at the wall surface which constitutes the casting surface of the mold cavity 11 and the other end exposed in the conduit 13. The inserts are made of a material which has high heat conductivity, such as copper, which is the preferred material. The wall 12 is made of a material which has a lower heat conductivity then the inserts. Steel is a suitable material for the wall I2.

In conventional continuous-casting molds the wall defining the mold cavity, or at least the casting surface thereof, is usually entirely of copper, and the casting process rapidly wears the copper. An additional advantage of the mold construction of the present invention is that the wall 12 may be made of, or at least lined with, a material such as steel which has good wear resistance as compared to copper. Thus, a mold in accordance with this invention, wherein only the inserts 20 are copper and the rest of the casting surface is of relatively wear-resistant material, has a much longer service life than conventional copper-lined molds.

As illustrated in FIG. 2, the inserts 20 are spaced around the circumference of the mold cavity II over the length of the wall 12, the spacing being determined by the size of the inserts and the rate of heat transfer desired for a given area of the casting surface. It is also desirable to have the thickness of the solidified shell 18 substantially unifonn around its circumference by the time the strand 17 reaches the lower end of the mold cavity 11 and emerges therefrom. Accordingly, in a preferred form of the mold indicated in FIG. 2 inserts 20 are arranged in a staggered pattern in rows over the length of the mold cavity so that, along any given line parallel to the longitudinal axis of the mold cavity along the casting surface from one end of the mold cavity to the other, the total length of that portion of the casting surface provided by the ends of successive inserts traversed by said line will be substantially the same as for any other such line, around the circumference of the mold cavity. Consequently, the total amount of heat extracted from metal moving through the mold cavity 11 will be substantially the same at all points around the periphery of the metal by the time the metal reaches the lower end of the mold cavity so that the shell 18 will have a substantially uniform thickness around its circumference as the strand 17 leaves the mold.

As illustrated in FIGS. 3, 4 and 6, the ends of the inserts 20 exposed at the casting surface of the wall are coplanar with the casting surface. Their other ends, 200 or 20b respectively, may extend into the conduit 13 and be enlarged to increase the rate of heat transfer from the inserts 20 to the coolant circulated through the conduit, as shown in FIGS. 3, 4 and 5, or may be coplanar with the inner surface of mold wall 12, as shown in FIG. 6.

The provision of inserts 20 of copper, or other material having a similarly high heat conductivity, in accordance with this invention, is also useful in static molds and in drum-type molds. In drum-type molds known in the art a drum, which is cooled by water circulated in the interior thereof, is rotated so that its periphery dips into a path of molten metal. Some of the metal adheres to and solidifies on the periphery of the drum in the form of a sheet which is peeled off continuously as the drum rotates. In contradistinction to an open-ended continuous-casting mold, such as the mold described above, with a drurn-type mold the solidifying metal would not move relatively past the exposed ends of the inserts to any appreciable extent; consequently, the exposed ends of the inserts could suitably be shaped to project slightly out from, or be indented with respect to, the adjacent drum surface.

It will be appreciated that the embodiments shown in the drawings and described above are examples of suitable forms of the invention and that some modifications may be made in the illustrated structure and arrangement of the elements without departing from the scope of the invention defined by the following claims.

I claim:

1. A continuous casting mold having an open-ended cavity extending therethrough surrounded by a wall, the inside surface of which defines a casting surface, a conduit for circulating coolant in contact with the outside surface of said wall, said wall being composed of first material and having multiple inserts of a second material mounted therein at spaced intervals, said second material having higher heat conductivity than the first, said inserts each extending through the wall with one end exposed at said casting surface and with its other end exposed in said conduit, said inserts being arranged in a pattern such that any linear portion of the casting surface parallel to the longitudinal axis of the mold cavity and extending from one end of the mold cavity to the other includes substantially the same total length and area of exposed insert surface as other similar linear portions at respectively difi'erent locations around the circumference of the casting surface. 

1. A continuous casting mold having an open-ended cavity extending therethrough surrounded by a wall, the inside surface of which defines a casting surface, a conduit for circulating coolant in contact with the outside surface of said wall, said wall being composed of first material and having multiple inserts of a second material mounted therein at spaced intervals, said second material having higher heat conductivity than the first, said inserts each extending through the wall with one end exposed at said casting surface and with its other end exposed in said conduit, said inserts being arranged in a pattern such that any linear portion of the casting surface parallel to the longitudinal axis of the mold cavity and extending from one end of the mold cavity to the other includes substantially the same total length anD area of exposed insert surface as other similar linear portions at respectively different locations around the circumference of the casting surface. 